This invention relates to bearing assemblies for journalling rotor shafts of high-speed rotary machines, particularly superchargers for automotive vehicles, and, more particularly, to a bearing assembly of the floating bush type serving as a bearing for journalling the rotor shaft of a supercharger.
Generally a supercharger is provided with bearings for journalling a rotor shaft against a radial load and a thrust load applied thereto. Various types of bearing have been proposed for use as bearings for journalling the rotor shaft against a radial load. The main stay of the bearings used for this purpose nowadays is a bearing of the floating bush type, as shown in U.S. Pat. No. 3,565,497, for example. The bearing of the floating bush type includes a floating bush interposed between the rotor shaft and a housing and restrained against movement axially of the rotor shaft by snap pins or other movement preventing means attached to the housing. The floating bush has a construction in which its inner peripheral portion positioned against the outer peripheral surface of the rotor shaft is of the same length as its outer peripheral portion.
Meanwhile there has in recent years been an increased demand for increasing the speed of supercharger and obtaining a compact size therein. However, although an attempt has been made to increase the speed of the supercharger by using floating bushes described hereinabove, it has been impossible to attain the end because vibration increases in the high-speed rotation range and the floating bushes suffer a burning loss and a frictional loss. Moreover, owing to the structural arrangement whereby the inner and outer peripheral portions of a floating bush are as closely spaced apart as possible from adjacent parts for minimizing vibration, the inner peripheral portion has a peripheral velocity of over 100 m/s and as a result an increase in frictional loss and further more scoring is inevitable.